Energizing circuit for the dc operating winding of an electromagnetic contactor or the like

ABSTRACT

An improved circuit for energizing and quickly deenergizing the DC operating winding of an electromagnetic contactor from sources of AC supply having a wide range of frequencies. It employs a full wave rectifier bridge, an auxiliary electromagnetic switch having a pair of low-inductance operating windings and normally open contacts. One of the auxiliary switch windings of high resistance is connected across the DC output terminals of the rectifier bridge while the other thereof of low resistance is connected across the same terminal in series with the normally open contacts and the operating winding of the electromagnetic contactor.

' United States Patent Inventors Werner B. llalbeck Cedarburg; John A.Quanl, Milwaukee, both 01, Wis. Appl. No. 14,445 Filed Feb. 26, 1970Patented July 20, 1971 Assignee Cutler-Hammer, lac.

Milwaukee, Wis.

ENERGIZING CIRCUIT FOR THE DC OPERATING WINDING OF AN ELECTROMAGNETICCONTAC'IOR OR THE LIKE 5 Claims, 5 Drawing Figs.

11.8.01. 317/123, 200/166 R, 335/129, 335/132, 335/151, 317/D1G. 6,317/1555 Int. Cl 11011! 47/02 Field ol'Smrch 317/123, 141, DIG. 6

[56] References Cited UNITED STATES PATENTS 2,279,849 4/1942 Warrington3 l7/DlG. 6 2,424,344 7/1947 Veinoff 321/8 2,472,553 6/1949Theunissen... 317/123 3,131,331 4/1964 Ray 317/123 3,200,302 8/1965Krebs et a1 317/141 3,239,627 4/1966 Davies et al. 335/ l 28 PrimaryExaminerLee T. Hix Attorney-Hugh R. Rather ABSTRACT: An improved circuitfor energizing and quickly deenergizing the DC operating winding of anelectromagnetic oontactor from sources of AC supply having a wide rangeof frequencies. It employs a full wave rectifier bridge, an auxiliaryelectromagnetic switch having a pair of low-inductance operatingwindings and normally open contacts. One of the auxiliary switchwindings of high resistance is connected across the DC output terminalsof the rectifier bridge while the other thereof of low resistance isconnected across the same terminal in series with the normally opencontacts and the operating winding of the electromagnetic contactor.

PATENTEUJULZOIQH 3 R94 614 SHEET 2 SP2 Jig. 4'

ENERGIZING CIRCUIT FOR THE DC OPERATING WINDING OF AN ELECTROMAGNETICCONTACTOR OR THE LIKE BACKGROUND OF THE INVENTION Compactelectromagnetic contactors and relays used in aircraft commonly employDC operating windings. This requires use of rectifiers between the ACsupply and the operating windings, with the latter normally connectedacross the output terminals of a full wave rectifier bridge. When the ACsupply to the rectifier bridge is interrupted the DC operating windingis rather slow in dissipating its stored energy resulting inslowto-release action of the contactor and its contacts.

To break contact welds, and prevent contact erosion resulting fromcontact bounce the contact opening force imparted through armaturereturn springs should act quickly and strongly. Hammer below likeinitial accelerating forces are desirable. It will be appreciated thatif the magnetic armature holding force decays slowly upon deenergizationof an operating winding the accelerating ability of the armature returnsprings will be commensurately debilitated.

It is a primary object of the present invention to provide an improvedcircuit for energizing the DC energizing windings of electromagneticcontactors from a source of AC supply.

A further object is to provide a circuit of the aforementioned typewhich is deenergized by quick release action of the contacts uponinterruption of the AC source to the operating coil and which is furthercharacterized by steady contact maintenance when the operating coil isenergized from AC sources having widely different operating frequencies.

Other objects and advantages of the invention will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic showing of aprior art circuit for energizing DC operating coils from a source ofalternating current supply.

FIG. 2 is a diagrammatic showing of an improved circuit made inaccordance with the invention for energizing the operating coils of suchcontactors.

FIG. 3 is a top view, with a cover and contacts removed, of ahermetically sealed electromagnetic contactor to which the circuit ofFIG. 2 is applied.

FIG. 4 is a view in transverse cross section of the contactor takenalong the line 4-4 of FIG. 3.

FIG. 5 is an exploded view of certain of the parts used in the improvedenergizing circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 depicts the arrangementheretofore commonly used in energizing the DC operating winding ofcontactor or relay from a source of AC supply. More particularly a DCelectromagnetic energizing coil 10 is connected across the outputterminals 120 and 12b of a full wave rectifier bridge 12 which alsocomprises half wave rectifier r, to r4. The AC input terminals 12c and12d are connected to AC supply lines 14 and I6 and a switch 18. Uponclosure of switch 18 rectified AC or pulsating unidirectional current issupplied to coil 10 to energize the same.

In certain applications involving the use of power relays and contactorssupplied from AC supply sources a prevalent slowto-release condition hasbeen found to exist upon opening of switch I8. This is due to slowdissipation of the magnetic energy stored in the field existing aboutcoil I0. It will be noted that upon opening of switch 18, the individualrectifiers in the bridge 12 immediately provide local circuits for flowof the induced current and is not dissipated by arcing at the contactsof switch I8.

FIG. 2 shows an improved circuit for energizing a DC operating windingof a power relay or contactor from an AC supply source which overcomesthe aforedescribed slow-torelease problem. More particularly it employsthe same rectifier bridge 12 and switch 18 as shown in FIG. I connectedto the AC supply through lines LI and L2. DC output terminal 12b of therectifier bridge is connected in series with the lowresistance,low-impedance coil 20a of a sensitive electromagnetic switch 20 whichpreferably has hermetically sealed reed switch contacts 20b. The otherend of coil 20a is connected in series with reed switch contacts 20b,and the DC electromagnetic operating coil 22a of a power contactor 22.As depicted contactor has another coil 22b, like coil 22a, which isconnected in series therewith. The main, high-resistance, low-inductanceoperating coil 200 of switch 20 is connected at one end to the pointcommon between terminal 12b and coil 20a, and is connected at its otherend to the point common between terminal 12a and coil 22b of contactor22.

When lines L1 and L2 are initially energized by closure of switch 18pulsating DC current flows from terminal 12b through coil 20c. If thefrequency of the AC voltage is applied to the rectifier bridge is 60Hz., the contacts 20c may tend to vibrate. However, when they initiallyclose this provides for current flow from terminal 12b through coil 20a,then closes contacts 20b and coils 22a and 22b to terminal 12a. The highinductance of the coils 22a and 22b prevents the current flowing in thelast mentioned circuit from approaching zero as a consequence of the ACinput voltage going to zero times each second. Accordingly theadditional ampere turns provided by coil 20a prevents the contacts 20bfrom opening. When the AC supply to bridge 12 is interrupted coil 20c,because of its low inductance, deenergizes rapidly to permit rapidopening of contacts 20b. The inductive energy stored in coils 20a and 22a and 22b is rapidly dissipated in arcing at contacts 20b when thelatter opens. Consequently, the contact drop out time of contactor 22 isconsiderably shortened from that obtainable from the circuit of FIG. I.

In a commercial version of a hermetically sealed contactor for use witheither 60 or 400 Hz. AC supply sources which will hereinafter bedescribed, the coils of switch 20 and contactor 22 were selected to havethe following values of resistance and inductance:

Coil 20a-7.98 ohms and 0.14 X10 henries Coil 20c-13.26 k. ohms and 0.59henries Coil 22a860 ohms and 58 henries and 22b (In Series) FIGS. 3 to 5disclose an embodiment of the circuit of FIG. 2

in a commercially available hermetically sealed electromagneticcontactor of the type disclosed in the Davies et al. US. Pat. No.3,239,627 which has been assigned to the assignee of the presentapplication. More particularly the contactor comprises a bottom casing30, a top cover 32 and a stationary magnet and coil assembly 34, anarmature 36, a control base 38, a movable contact assembly 40, maincontact terminals 42, coil contact terminals 44, and a rectifier pack46.

The coil and stationary magnet assembly comprises spaced apart paralleliron cores 48a and 48b which respectively have coils 48c and 48dwoundthereon. Coils 48c and 48d are connected together at adjacent endsthrough a conductor 50. The other end of coil 48c is connected through ashort conductor 52 to a terminal 540 of reed switch assembly 56. As bestshown in FIG. 5, switch assembly in addition comprises coil module 58, aglass encased reed switch 60, insulator blocks 62, an iron magnetic coilsurround member 64, a mounting bracket 66, and a second terminal 54b.

Coil module 58 comprises concentrically wound coils 58a and 58b, thatcorrespond respectively to coils 20a and 20c aforedescribed inconnection with FIG. 2, which are encased in molded epoxy casing 580 ofan elongated annular form. Module 58 is provided with a longitudinalclearance opening to accommodate the casing of reed switch 60. Module 58in turn closely fits with the interior wall of member 64 which providesa magnetic flux return path, and the external terminals 60aand 60bextend throughclearance openings in the insulator blocks 62. Terminals54a and 540 are soldered to the terminals 60a and 60band hold the.blocks 62 in abutting relation againstthe ends of casing 58. Two wireleads 58d and 58e extend out one end of module casing 58c, and asingle-wire lead 58f extends out of the other end thereof.

Member 64 is secured to the underside of the semicylindrical portion 660of mounting bracket 66, preferably by an insulating adhesive tape formedof Teflon. At one end bracket 68 has a outwardly turned flanges 66b of achannel-shaped mounting portion 660 which has a screw accommodatingopening 66d formed therein. The portion 66c seats within a notch formedin a molded support block 70 for the main coil assemblies and a screw 72takes into a threaded insert (not shown) to hold one end of bracket 66in place. The other end of bracket 66 is provided with two spacedparallel tongue portions 66c and 66f and an upwardly and outwardlycurved tongue 66g. The tongues 66c and 66f fit within complementaryopenings in the front armature and main coil supportplate 74.

' The tongue 66g hooks over a tang 74a a struck and bent out of I outputterminal 46b (not shown) of rectifier pack 46. Lead 58f which internallyof casing 58c is connected to the other end of coil 58a is connectedtogether with terminal 60a of reed switch 60 to terminal 54b. Theterminal 60bof reed switch 60 is connected to terminal 54a, and thelatter as aforementioned is connected through lead 52 to one end of mainoperating coil 48c. The lead 58c which internally of casing 58c isconnected to the other end of coil 58b is connected by a wire lead 78 toa lead 80 with which it is electrically bonded. Lead 80 at one end isconnected to the negative DC output terminal 46a of rectifier pack 46,and at its other end has connection with the other end of main operatingcoil 46d.

Rectifier pack 46 has external AC input terminals 46c and 46d that areconnected through wire leads to the coil input terminals 44. lntemallyit may be assumed that rectifier pack 46 comprises a full wave set ofpower half wave rectifiers (not shown) electrically connected togetherand to AC input terminals 46a and 46b and DC output terminals 46c and46d as depicted for full wave rectifier l2 in FIG. 2. Such rectifiersand interconnections are preferably molded in situ in a suitableinsulating compound to form a molded casing 46c. Rightangle mountingbrackets 46c which have one leg of each thereof molded in place incasing 46f are spot welded at their other legs to the inner wall ofcasing 30.

lthas been found that the improved energizing circuit hereinbeforedescribed works well with either 60 or 400 Hz. AC supply sources andprovides quick contact drop out operation of the main contactor. Whilethe circuit has been described in conjunction with contactors having twoseries connected main operating coils, it will work equally well withcontactors or relays having a single-operating coil.

I claim:

' '1. In combination:

a. a full wave rectifier bridge having input terminals for connection toand disconnection from a source of alternating potential and a pair ofunidirectional current output terminals; v

b. a first electromagnetic device having an energizing coil;-

c. a second electromagnetic device having a first energizingcoilconnected across the rectifier bridge output terminals, a secondenergizing coil, and normally open contacts connected in series withsaid second energizing coil and the energizing coil of said firstelectromagnetic device across said rectifier bridge output terminals;

d. said coils of said second electromagnetic device having inductivetime constants substantially less than that of the energizing coil ofsaid first electromagnetic device to afford, upon interruption of inputpotential to said bridge, rapid opening of ts associated contacts andsubsequent rapid dissipation of stored inductive energy in theenergizing coil'of said first electromagnetic device.

2. The combination according to claim 1, wherein said first energizingcoil of said second electromagnetic device is of high resistance andsaid second energizing coil is of low resistance and both are ofrelatively low inductance compared to the energizing coil of said firstelectromagnetic device.

3. The combination according to claim 1, wherein the normally opencontacts of said second electromagnetic are of the enclosed reed switchtype and wherein said first and second energizing coils areconcentrically disposed about said reed switch.

4. The combination with an electromagnetic contactor or the like havinga pair of parallel, spaced apart operating coils and a movable armature,of means for energizing said coils with unidirectional current derivedfrom a source of AC supply, comprising:

a. a full wave rectifier bridge;

b. an auxiliary electromagnetic switch having contacts sealed within acasing, first and second energizing coils concentrically disposed aboutsaid casing with the first coil connected directly across the outputterminals of said rectifier bridge and the second coil connected inseries with its associated contacts and the series connected operatingcoils of said contactor across said output terminals;

c. said auxiliary electromagnetic switch being disposed in proximity toand between said operating coils of said contactor.

5. The combination according to claim 4 wherein the auxiliary switchenergizing coils are encapsulated in an annular nonmagnetic casing andthe switch contacts are in a sealed envelope disposed within saidannular casing, and wherein the auxiliary switch assembly is surroundedby an annular iron member.

ggg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,594,614 Dated July 20, 1971 Inventor(s) Werner B. Halbeck & John A.Quaal It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Column 2, line 18, "is" should be omitted;

line 42, "10 should be --10 line 67, "surround" should be-surrounding--.

Column 3, line 11, "a" (first occurrence) should be -an-- and "flanges"should be -flange--;

line 21, "a" (second occurrence) should be omitted.

Column 4, line 26, "electromagnetic" should be --electromagnet- Si nedand sealed this 28th day of March 1 972.

(SEAL) Attest:

L EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK J Attesting OfficerCommissioner of Patents

1. In combination: a. a full wave rectifier bridge having input terminals for connection to and disconnection from a source of alternating potential and a pair of unidirectional current output terminals; b. a first electromagnetic device having an energizing coil; c. a second electromagnetic device having a first energizing coil connected across the rectifier bridge output terminals, a second energizing coil, and normally open contacts connected in series with said second energizing coil and the energizing coil of said first electromagnetic device across said rectifier bridge output terminals; d. said coils of said second electromagnetic device having inductive time constants substantially less than that of the energizing coil of said first electromagnetic device to afford, upon interruption of input potential to said bridge, rapid opening of its associated contacts and subsequent rapid dissipation of stored inductive energy in the energizing coil of said first electromagnetic device.
 2. The combination according to claim 1, wherein said first energizing coil of said second electromagnetic device is of high resistance and said second energizing coil is of low resistance and both are of relatively low inductance compared to the energizing coil of said first electromagnetic device.
 3. The combination according to claim 1, wherein the normally open contacts of said second electromagnetic are of the enclosed reed switch type and wherein said first and second energizing coils are concentrically disposed about said reed switch.
 4. The combination with an electromagnetic contactor or the like having a pair of parallel, spaced apart operating coils and a movable armature, of means for energizing said coils with unidirectional current derived from a source of AC supply, comprising: a. a full wave rectifier bridge; b. an auxiliary electromagnetic switch having contacts sealed within a casing, first and second energizing coils concentrically disposed about said casing with the first coil connected directly across the output terminals of said rectifier bridge and the second coil connected in series with its associated contacts and the series connected operating coils of said contactor across said output terminals; c. said auxiliary electromagnetic switch being disposed in proximity to and between said operating coils of said contactor.
 5. The combination according to claim 4 wherein the auxiliary switch energizing coils are encapsulated in an annular nonmagnetic casing and the switch contacts are in a sealed envelope disposed within said annular casing, and wherein the auxiliary switch assembly is surrounded by an annular iron member. 